text: Multiple factors produced by the environment stimulate the corrosion and deterioration of concrete, such as freezing conditions, radiation exposure, and extensive heat cycles or freeze-thaw and wet-dry cycles. Cycles that cause mechanical breakdowns of concrete, such as freeze-thaw cycles, are incredibly ruinous. All these provide ways for microbes to take over, further eroding and weakening structures made of concrete. An uptick in damages on urbanized sewer systems and cities that line the coast has forced people to look further in-depth at how to preserve concrete from microbes. 
  To halt the damage done by microbes, a complete comprehension of corrosion-causing microbes must be undertaken. This includes knowing what the specific microbes and their community are made up of and how they break down structural concrete. Environmental stressors on structures often promote microbial corrosion caused by bacteria, Archaea, algae, and fungi. These microorganisms depend on their environment to provide proper moisture, pH levels, and resources that allow reproduction. 
  The pH level of concrete greatly influences what microbes can reproduce and how much damage is done to the concrete. A concrete surface is alkaline, making it difficult for microbes to germinate. However, chemical processes by the environment and microorganisms themselves cause changes in the concrete. Environmental conditions combined with carbonization caused by select microbes fabricate negative changes in the pH of the concrete. These few microbes can excrete metabolites that change the pH from 12 to 8. With a lower pH level, more microorganisms can survive on the concrete, thus quickening the corrosion rate. This becomes an extreme problem, as many microbes that attack concrete survive in anaerobic conditions. Sewers, for example, have low oxygen levels and are high in nitrogen and sulfuric gas, making them perfect for microbes that metabolize those gases.